Method of refining oil with a solvent



Dec-'19, 1950 G. B. ARNOLD ETAL METHOD 0F REFINING OIL WITH A SOLVENTFiled Sept. 30, 1947 Il luiila;

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Patented Dec. 19, 1950 METHOD OF REFINING OIL WITH A SOLVENT George B.Arnold, Glenham, and William E. Skelton, Beacon, N. Y., sssignors to TheTexas Company, New York, N. Y., a corporation of Deiaware ApplicationSeptember 30, 1947, Serial No. 777,072

This invention relates to a method of refining oil with a solvent liquidwhich is at least partially miscible with water at ordinary temperaturesand particularly relates to the extraction of oil containingconstituents whose true boiling point is lower than or inthe sameboiling range `as that of the solvent.

In accordance with the invention, a relatively low boiling feed oil,such as kerosene, is extracted with a selective solvent, such asfurfural, in the presence of a small amount of water and underconditions effective to form extract and railinate phases respectively.The raffinate phase comprises non-aromatic or relatively insolubleconstituents of the oil mixed with a small proportion of the solvent andwater. The extract phase comprises the relatively aromatic andnaphthenic constituents of the oil dissolved in the main body of aqueoussolvent.

The extract and raffinate phases are advantageously separately subjectedto distillation so as to effect separation of solvent from oil. It iscontemplated supplying suilcient steam or water to the fractionatingzone in which the raffinate phase is distilled to form a ternarywater-oilsolvent azeotrope with all of the solvent present in therailinate phase mixture. The resulting distillate is condensed andsubjected to settling to form oil-rich, water-rich and solvent-richliquid layers respectively. The oil-rich liquid is removed and treatedto recover a small amount of residual solvent retained therein or may berecycled to the distillation zone. 'I'he solvent-rich liquid is recycledto the extraction zone. The water-rich liquid is used in part asreiluxliquid in the raffinate phase fractionating zone, and the remaindertreated4 to recover the small amount of solvent retained therein.

The extract phase obtained from the extraction zone is distilled in aseparate fractionator to the extraction zone advantageously to the u 90%'f.-

upper portion thereof or with fresh solvent 6 Claims. (Cl. 1915-1436) 2while the water-rich liquid is recycled to the extract phasefractionating zone.

The residual liquid comprising the main body of solvent, and extract oilis conducted from the extract phase fractionating zone to a secondaryfractionating zone wherein the remaining extract oil is azeotropicallydistilled from the solvent and treated in a manner substantially similarto that disclosed in our co-pending application Serial No. 777,071,filed September 30, 1947, and which will be described in more detaillater.

The invention thus involves recovering solvent as a distillate from theramnate oil phase and as an oil-free or substantially oil-free liquidresidue from the extract phase.

The invention is particularly applicable to the solvent treatment of lowboiling oils such as kerosene or fractions of petroleum boiling in therange of about 300 to 6501F. ASTM and comprising constituents which formrelatively low boiling azeotropes with the solvent and water. A featureof the invention is that only a small proportion of the total solventflowing through the process is vaporized in the recovery of the solventfrom the oil. As a result, the solvent is subjected to less severetemperatures and therefore subject to less decomposition. Furthermore,where the true boiling point range of the oil includes the boiling pointof the solvent, ysimple fractionation is ineffective to separate the oiland solvent.

A distinguishing feature of the present invention over that disclosed inthe previously mentioned co-pending application is that the solvent isrecovered from the extract phase mixture in a two-stage ternaryazeotrope system, and that the oil recovered in the first ternaryazeotrope is recycled to the extraction zone as extract recycle.Recycling of this particular oil to the extractionV zone facilitatesobtaining a higher yield of high quality raiiinate oil and a, higherquality extract.

In order to illustrate the invention in more detail, reference will nowbe made to the accompanying drawing comprising a flow; diagram of theprocess as applied to1the treatment of kerosene. The feed oil has an APIgravity of about 40.4 and has an ASTM boilin'g range as follows:

I. B. P. 332 10% 365 20% 377 tower through a pipe 4. The solventcomprises furfural and minor amounts of water and oil as a result ofprevious use in the process. It thus contains about 15.0% oil and 3.0%water by volume. It is introduced to the tower in the proportion ofabout 1 volume of solvent to 2 volumes of feed oil. The temperatures ofthe entering streams of oil and solvent are regulated, so that thetemperature at the bottom of the tower is maintained at about 100 F.,while the temperature at the top is maintained at about 150 F.

Under these conditions, extract and railinate -phases are formed. Theraiflnate phase comprises oil amounting to from about 60 to 80% byvolume of the feed oil. The rafilnate phase is continuously removed fromthe upper portion of the tower 3 through a pipe 5 and heat exchanger -6to a fractionator 'I. Heat may be supplied tothe bottom of thefractionator either with open steam, a closed heating coil, or acombination of both. As will be mentioned later, provision is made forsupplying reflux liquid to the top of the tower. Suiicient water isintroduced to the tower either in the form of steam or water reflux orboth to form the ternary Water-oil-furfural azeotrope with all of thefurfural present in the raftlnate phase feed. The top of this tower ismaintained at a temperature of about 205 to 250 F., and the bottom at atemperature of about 250 to 400 F., so that the solvent is completely orsubstantially completely distilled from the raillnate oil, thesolventfree oil being discharged through a pipe 8.

The distillate comprising solvent, water, and a small amount of oil isremoved through pipe 9 into condenser I0 to a settling chamber Il. Thesettler is maintained at a temperature of about '70 to 150 F., and thecondensate separates into oil-rich, water-rich, and solvent-rich liquidlayers respectively. These layers have the following approximatecomposition:

The solvent-rich liquid is continuously drawn of! through pipe I2 whichcommunicates with pipe 4 by which this liquid is recycled to theextraction tower 3.

The oil-rich liquid is drawn oi from the top of the settling chamberthrough a pipe I3. If not recycled to tower 1, it is passed to asecondary fractionator Il wherein it is subjected to azeotropicdistillation, suiiicient water being injected into the fractionatoreither inthe form of open steam or water reflux to form the ternaryazeotrope of furfural, oil, and water, the operation of thisfractionator being conducted so as to eilect recovery of raillnate oilfrom the oil-rich liquid. The recovered oil is discharged through pipeI6, while the distillate from this fractionator is recycled through apipe I1 to the settling chamber II. The oil discharged through 4 pipe II has the following approximate characteristics:

API gravity 46.0

ASTM distillation:

I. B. P. 271 10% 315 20% 327 50% 374 445 E. P. 502

The Water-rich liquid is drawn of! through pipe 2II, and at least aportion thereof diverted through pipe 2| for recycling to the top ot thefractionator 'I as reiiux liquid. The non-recycled portion of thisliquid can be separately treated to recover residual furfural and anyoil therefrom. On the other hand, and as will be described later, it maybe conducted through pipe 22 for treatment with water-rich liquidrecovered from the treatment of the extract phase to whichreference willbe made later.

The extract phase collecting in the bottom of the extraction tower 3 iscontinuously drawn olf through pipe 30 to a primary extract -phasefractionator 3l. This fractionator is also provided with means Iorsupplying heat to the bottom thereof, either in the form of open steamor a closed heating coil or both, provision being made also for theintroduction of reflux liquid. Suillcient water is injected into thefractionator to form a ternary furfural-oil-water azeotrope with a minorportion of the extract oil. This azeotrope is thus removed as adistillate through pipe 32 and a condenser 33 from which it is passed toa settling chamber 34 wherein it separates into oil-rich, water-rich andsolvent-rich liquid layers respectively.

The solvent-rich liquid is drawn of! through pipe 35 which communicateswith pipe 4 for return to the extraction zone. 'I'he water-rich liquidis drawn oi through pipe 36 and recycled as reflux to the fractionatorII.

The oil-rich liquid is drawn of! through pipe 31 and heat exchanger 3Ufrom which it is discharged through a plurality of branch pipes 39 and35-A for introduction at one or more intermediate points of theextraction tower.

The amount of oil injected through pipes 33 and 39-A will depend uponthe nature of the feed oil, the extraction temperature, and the degreeof solvent fractionation desired. Usually, it will amount to about 1.0to 10.0% by volume of the feed oil. The injected oil is the relativelyparailinic portion of the extract and will have the followingapproximate characteristics:

API gravity 47.1

ASTM distillation:

I.B.P. 268 10% 310 20% 330 50% 375 90% 443 E. P. 512

form of'steam or redux is injected through iractionator 3| to form theternary oil-furiural-water azeotrope with substantially all of theextract oil present in the feed stream flowing through pipe I0. Thetemperature at the top of the fractionator will be about 205 to 250 F.and that at the bottom will be about 250 to 400 Il'. The amount of water.required for forming they azeotrope is about 5 to 50% by volume of thefeed mixture flowing through pipe 40.

Substantially oil-free solvent is drawn oi! from the bottom offractionator 4i through pipe l! which communicates with pipe 4.

The resulting distillate containing extract oil is conducted throughpipe Il and condenser M to a settling chamber 45 maintained at. about 70to 150 F. Separation into oil-rich, water-rich and solvent-rich liquidlayers occurs. The solvent-rich liquid is drawn oil' through pipe I5 andconducted through pipe I.

The oil-rich liquid is drawn of! through pipe 41 and introduced to atertiary fractionator Il substantially similar to the precedingfractionator. In this fractionator, the residual solvent retained in theoil-rich liquid is distilled therefrom as an azeotrope. The resultingdistillate is advantageously recycled through pipe 50 to the settlingchamber 45.

The water-rich liquid from chamber I5 is drawn oil' through pipe 5I and,in part, used as reflux in fractionator 48, and, in part, as reflux infractionator 4I.

The solvent-free extract oil is discharged from iractionator Il throughpipe 55.

The extract oil discharged through pipe 5l is of the followingcharacter:

As previously mentioned, some of the water- 4rich liquid obtained in thesettler Il can be drawn oil! through pipe 22 and added to the liquiilowing through pipe 5I.

In the event that there is surplus water-rich liquid from the settler 34beyond that required for reiiuxing the i'ractionator 3|, this surplusliquid can also be passed to fractionator 45.

In order to avoid -a build-up of water in the system. provision may bemade i'or diverting a portion of the water-rich liquid from settler l5through pipes 5I and 5l, and subjecting the diverted stream to strippingin a separate fractionawr so as to strip the small amount of retainedsolvent from the excess water which latter can then be dicharsed.

While the treatment of kerosene has been speciilcally referred to inconnection with the drawing, nevertheless, it should be understood thatthe process is applicable to the treatment of other types of oils andalso to the treatment of sus oil contamina. usually in small amounts.constituents having a true boiling point lower than or in the sameboiling range as that of the solvent used. In general, it hasapplication to the treatment of hydrocarbon mixtures having an ASTMboiling range o! about 275 to 600 l". It is also contemplated that ithas applica; tion to the treatment o! oils derived from animal andvegetable sources. Specino conditions of 'temperature and solvent dosagemay vary from those specincally mentioned, depending on the character ofthe feed oil undergoing treatment and the degree of fractionalseparation desired in the extraction tower 3.

'Ihe invention is particularly concerned with the use of relatively highboiling organic solvent liquids which are miscible, at least to someextent with water, and with which constituents of the oil feed in thepresence of water form azeotropes. Selective solvents other thanfuriural may be used. They may include other derivatives of the turangroup and other aldehydes such as benzaldehyde nitrobenzene and ketones,etc.

Obviously many modifications and variations of the invention as aboveset forth may be made without departing from the spirit and scopethereof, and therefore only such limitations should be imposed as areindicated in the appended claims.

We claim:

' l. In the solvent refining of feed oil of the class consisting ofkerosene and gas oil containing at least a small proportion of naturallyoccurring constituents having true boiling points in the range o! thesolvent boiling temperature and below wherein the feed oil is subjectedto contact in an extraction tower in the presence oi.' water with awater miscible organic solvent liquid having selective solvent action asbetween parailinic and non-paraftlnic constituents of the oil, extractand raillnate phases respectively lean and rich in paralnic constituentsof the oil are formed, said phases separately removed from theextraction zone. each of said removed phases comprising oil, solvent andwater. and the removed phases treated to recover solvent from the oilfor reuse in the extraction zone, the method comprising recoveringsolvent from the removed raiilnate phase. recycling so-recovered solventto the extraction zone, separately distilling from said extract phase inthe presence of added water in a primary fractionating zone, adistillate containing ternary azeotrope of solvent, oil and water, theoil in said azeotrope being the relatively paraillnic portion of theextract oil and amounting to a relatively minor proportion of theextract oil, and forming a residual liquid fraction comprising the mainbody of solvent liquid contained in the extract phase removed from theextraction zone and in addition the remainder and major portion of theextract oil, substantially completely condensing said primarydistillate, subjecting resulting condensate to settling in a primarysettling zone thereby forming oil-rich, water-rich and solvent-richliquid layers respectively, said oil-rich layer comprising substantiallyall of said azeotrope oil, recycling said oil-rich layer to the extractphase zone of the extraction tower, recycling said solvent-rich layer tothe ratilnate zone of said extraction tower, recycling at least aportion of the water-rich layer as redux to the primary fractionatingzone, passing said residual liquid fraction to a second fractionatingzone, subjecting it therein to distillation in the presence of water toform a second distillate of ternary aseotrope containing substantiallyall of the remaining extract oil, and a second residual liquid fractioncomprising substantially assises densing said secondary distillate andseparately recovering extract oil and residual solvent therefrom.

2. The method according to claim 1 in which the solvent liquid isfurfural.

3. The method according to claim 1 in which the parafllnic oil containedin the first-mentioned ternary azeotrope amounts to about 1 to 10% byvolume of the feed oil passing to the extraction zone.

4. The method according to claim 1 in which the solvent comprisesfurfural and in which the relatively parailinic oil contained in thesaid first-mentioned azeotrope amounts to about 1 to by volume of thefeed 011 passing to the extraction mne.

5.'In the solvent refining of feed oil of the class consisting ofkerosene and gas oil containing at least a small proportion of naturallyoccurring constituents having true boiling points in the range of thesolvent boiling temperature and below wherein the feed oil subjected tocontact in an extraction tower in the presence of water with a watermiscible organic solvent liquid having selective solvent action asbetween paraiiinic and non-parainic constituents of the oil, extract andraffinate phases are formed, respectively lean and rich in parafllnicconstituents of the oil, said phases separately removed from theextraction zone, each of said removed phases comprising oil, solvent andwater, and the removed phases treated to recover solvent from the oilfor re-usein the extraction zone, the method comprising recoveringsolvent from the removed raflinate phase, recycling so recovered solventto the extraction zone, separately distil'ling from said extract phasein the presence of added water in a primary fractionating zone, adistillate containing ternary azeotrope of solvent, oil and Water, theoil in said azeotrope being the relatively parailinic portion of theextract oil and amounting to a relatively minor proportion of theextract oil and forming a residual liquid fraction comprising the mainbody of solvent liquid contained in the ex- 8 of said azeotrope oil,recycling said oil layer to the extract phase zone of the extractiontower, recycling said solvent-rich layer to the raflinate zone of saidextraction tower, recycling at least a portion of the water-rich layeras reflux to the primary fractionating zone, passing said residualliquid fraction to a second fractionatim;

tract phase removed from the extraction zone resulting condensate tosettling in a primary y settling zone thereby forming oil-rich,waterrich and solvent-rich liquid layers respectively, said oil-richlayer comprising substantially all zone, subjecting it therein todistillation in the presence of water to form a second distillate ofternary azeotrope containing substantially all of the remaining extractoil, and a second reside ual liquid fraction comprising substantiallyoil,- free solvent, said oil-free solvent being the bulk of the solventremoved from the extraction zone in the extract phase, returning saidoil-free solvent fraction to the extraction zone, condensing saidsecondary distillate, subjecting resulting secondary condensate tosettling'in a secondary settling zone, forming in said secondarysettling zone secondary oil-rich, solvent-rich and waterrich liquidliquid layers respectively, recycling secondary water-rich liquid inpart as reflux to said secondary fractionating zone, stripping residualsolvent from the remainder of said sec'- l ondary water-rich liquid,recycling secondary solvent-rich liquid to the extraction tower, passingthe secondary oil-rich liquid to a tertiary fractionating zone,distilling therefrom a ter#l tiary distillate containing solvent andleaving a substantially solvent-free extract oil as residual liquid,discharging said solvent-free extract oil and recycling said tertiarydistillate to said secondary settling zone.

6. The method according to claim 5 in which the solvent liquid comprisesfurfural.

GEORGE lles. ARNOLD.' WILLIAM E.' srmL'roN. i

REFERENCES CITED The following references are of record in the ille ofthis patent? v UNITED STATES PATENTS Number Name Date 2,139,240McFarland Dec. 6, 1 938 2,154,189 Weir Apr. 11, 1939 2,154,372 BosingApr. 11, 1939 2,167,731 Smoley Aug. l, 1939 2,168,570 Kraft Aug. 8, 19392,216,933 Atkins Oct. 8, 1940 2,381,996 Bloomer Aug. 15, 1945 2,465,959Tindall Mar. 29, 1949

1. IN THE SOLVENT REFINING OF FEED OIL OF THE CLASS CONSISTING OFKEROSENE AND GAS OIL CONTAINING AT LEAST A SMALL PROPORTION OF NATURALLYOCCURRING CONSTITUENTS HAVING TRUE BOILING POINTS IN THE RANGE OF THESOLVENT BOILING TEMPERATURE AND BELOW WHEREIN THE FEED OIL IS SUBJECTEDTO CONTRACT IN AN EXTRACTION TOWER IN THE PRESENCE OF WATER WITH A WATERMISCIBLE ORGANIC SOLVENT LIQUID HAVING SELECTIVE SOLVENT ACTION ASBETWEEN PARAFFINIC AND NON-PARAFFINIC CONSTITUENTS OF THE OIL, EXTRACTAND RAFFINATE PHASES RESPECTIVELY LEAN AND RICH IN PARAFFINICCONSTITUENTS OF THE OIL ARE FORMED, SAID PHASES SEPARATELY REMOVED FROMTHE EXTRACTION ZONE, EACH OF SAID REMOVED PHASES COMPRISING OIL, SOLVENTAND WATER, AND THE REMOVE PHASES TREATED TO RECOVER SOLVENT FROM THE OILFOR REUSE IN THE EXTRACTION ZONE, THE METHOD COMPRISING RECOVERINGSOLVENT FROM THE REMOVED RAFFINATE PHASE, RECYCLING SO-RECOVERED SOLVENTTO THE EXTRACTION ZONE, SEPARATELY DISTILLING FROM SAID EXTRACT PHASE INTHE PRESENCE FO ADDED WATER IN A PRIMARY FRACTIONATING ZONE, ADISTILLATE CONTAINING TERNARY AZEOTROPE OF SOLVENT, OIL AND WATER, THEOIL IN SAID AZEROTROPE BEING THE RELATIVELY PARAFFINIC PORTION OF THEEXTRACT OIL AND AMOUNTING TO A RELATIVELY MINOR PROPORTION OF THEEXTRACT OIL, AND FORMING A RESIDUAL LIQUID FRACTION COMPRISING THE MAINBODY OF SOLVENT LIQUID CONTAINED IN THE EXTRACT PHASE REMOVED FROM THEEXTRACTION ZONE AND IN ADDITION THE REMAINDER AND MAJOR PORTION OF THEEXTRACT OIL, SUBSTANTIALLY COMPLETELY CONDENSING SAID PRIMARYDISTILLATE, SUBJECTING RESULTING CONDENSATE TO SETTLING IN A PRIMARYSETTLING ZONE THEREBY FORMING OIL-RICH, WATER-RICH AND SOLVENT-RICHLIQUID LAYERS RESPECTIVELY, SAID OIL-RICH LAYER COMPRISING SUBSTANTIALLYALL OF SAID AZEOTROPE OIL, RECYCLING SAID OIL-RICH LAYER TO THE EXTRACTPHASE ZONE OF THE EXTRACTION TOWER, RECYCLING SAID SOLVENT-RICH LAYER TOTHE RAFFINATE ZONE OF SAID EXTRACTION TOWER, RECYCLING AT LEAST APORTION OF THE WATER-RICH LAYER AS REFLUX TO THE PRIMARY FRACTIONATINGZONE, PASSING SAID RESIDUAL LIQUID FRACTION TO A SECOND FRACTIONATINGZONE, SUBJECTING IT THEREIN TO DISTILLATION IN THE PRESENCE OF WATER TOFORM A SECOND DISTILLATE OF TERNARY AZEOTROPE CONTAINING SUBSTANTIALLYALL OF THE REMAINING EXTRACT OIL, AND A SECOND RESIDUAL LIQUID FRACTIONCOMPRISING SUBSTANTIALLY OIL-FREE SOLVENT, SAID OIL-FREE SOLVENT BEINGTHE BULK OF THE SOLVENT REMOVED FROM THE EXTRACTION ZONE IN THE EXTRACTPHASE, RETURNING SAID OILFREE SOLVENT FRACTION TO THE EXTRACTION ZONE,CONDENSING SAID SECONDARY DISTILLATE AND SEPARATELY RECOVERING EXTRACTOIL AND RESIDUAL SOLVENT THEREFROM.